Police are looking for anyone who was travelling between Swindon and Devizes on July 29 and may have seen the incident which forced a car off the road at around 6.20pm on the A4361 just before the Berwick Bassett bends.
A grey Vauxhall Corsa was heading towards Avebury when it met a white van which was overtaking a car in the opposite direction.
The Corsa was forced off the road and flipped on to its roof while the van carried on with its journey.
PC Mayhew, an off-duty road traffic officer, was on his way home from work when he arrived at the scene.
He said: "Luckily, the driver only had minor injuries but this could have been more serious.
"Whilst I managed to speak to some of the cars who stopped, a number of them left when they found out the driver was ok.
"It's vital that I speak to them as they may have dashcam footage or further evidence to identify the van which failed to stop."
If you were in the area, call 101 quoting the date and log number 0242. You can also report online here https://crowd.in/VU7bSr .